1. Field of the Invention
The present invention is related to a compensation circuit and method thereof, and particularly to a compensation circuit and method thereof that can compensate color shift that occurs when performing a color sequential display method.
2. Description of the Prior Art
Utilizing a color sequential display method to display red, green, and blue light of a display panel eliminates the need for color filters to display the red, green, and blue light of the display panel. A color mix theory of the color sequential display method forms predetermined colors by rapidly switching backlight corresponding to the red, green, and blue light, so that red, green, and blue light sub-pixels are shown during a frame interval. Please refer to FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D. FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D are diagrams illustrating a pixel of a frame displaying red, green, blue, and white light, respectively. As shown in FIG. 1A, when the pixel displays the red light, a liquid crystal LCR corresponding to a red sub-pixel of the pixel of the frame is turned on (liquid crystals LCG and LCB corresponding to green and blue sub-pixels of the pixel of the frame are turned off). Thus, the pixel can display the red light, where backlights BLR, BLG, and BLB corresponding to the red, green, and blue sub-pixels are turned on. Similarly, as shown in FIG. 1B, when the pixel displays the green light, the liquid crystal LCG corresponding to the green sub-pixel of the pixel of the frame is turned on (the liquid crystals LCR and LCB corresponding to the red and blue sub-pixels of the pixel of the frame are turned off). Thus, the pixel can display the green light. Similarly, as shown in FIG. 1C, when the pixel displays the blue light, the liquid crystal LCB corresponding to the blue sub-pixel of the pixel of the frame is turned on (the liquid crystals LCR and LCG corresponding to the red and green sub-pixels of the pixel of the frame are turned off). Thus, the pixel can display the blue light. As shown in FIG. 1D, when the pixel displays the white light, the liquid crystals LCR, LCG, and LCB corresponding to the red, green, and blue sub-pixels are turned on. Thus, the pixel can display the white light.
Please refer to FIG. 2A and FIG. 2B. FIG. 2A is a diagram illustrating the liquid crystals LCR, LCG, and LCB corresponding to the red, green, and blue sub-pixels being turned on persistently, and FIG. 2B is a diagram illustrating the liquid crystal LCR corresponding to the red sub-pixel changing from turning-off to turning on. As shown in FIG. 2A, because the liquid crystals LCR, LCG, and LCB corresponding to the red, green, and blue sub-pixels are turned on persistently (that is, the liquid crystals LCR, LCG, and LCB are turned on completely), luminances of the red, green, and blue sub-pixels can be 100% (that is, luminance of the white sub-pixel can also be 100%). As shown in FIG. 2B, when the pixel displays the red light, the liquid crystal LCR corresponding to the red sub-pixel of the pixel changes from turning-off to turning on. However, due to insufficient response time of the liquid crystal LCR, the liquid crystal LCR is not turned on completely when the backlight BLR is turned on, resulting in the luminance of the red sub-pixel being lower than 100% (such as 70%). Please refer to FIG. 2C. FIG. 2C is a diagram illustrating the liquid crystals LCR, LCG, and LCB corresponding to the red, green, and blue sub-pixels changing from turning-off to turning on when the pixel displays the white light. As shown in FIG. 2C, when a liquid crystal control voltage VC changes from 0% to 100%, the liquid crystals LCR, LCG, and LCB corresponding to the red, green, and blue sub-pixels change from turning-off to turning on. However, due to insufficient response time of the liquid crystals LCR, LCG, and LCB, the luminances of the red, green, and blue sub-pixels are different (such as 50%, 95%, 100%). As shown in FIG. 2C, duty cycles of the backlights BLR, BLG, and BLB corresponding to the red, green, and blue sub-pixels are 75%. Thus, the display panel may exhibit uneven color levels.
Please refer to FIG. 3A and FIG. 3B. FIG. 3A and FIG. 3B are diagrams illustrating the prior art solution to the problem of the uneven color levels of the display panel. As shown in FIG. 3A, the prior art utilizes shorter turning-on time of the backlights BLR, BLG, and BLB to solve the problem of the uneven color levels of the display panel, where the luminances of the red, green, and blue sub-pixels can reach 80%, 99%, and 100%, respectively. However, because the turning-on times of the backlights BLR, BLG, and BLB are shorter (the duty cycles of the backlights BLR, BLG, and BLB are 25%), the instantaneous luminances of the red, green, and blue sub-pixels must be increased to meet luminance requirements of the display panel, resulting in instantaneous output power being too high. In addition, as shown in FIG. 3B, the prior art inserts a black frame before each sub-pixel, so start points of the all color levels of the display panel are the same. But, as shown in FIG. 3B, the prior art reduces greatly the luminances of the red, green, and blue sub-pixels (such as 40%, 40%, and 40%). Therefore, the above mentioned prior arts for solving the problem of the uneven color levels of the display panel are not good choices for a designer of the display panel.